Photoelectric control apparatus for diaphragms



BLANHNER Au 252 'Ex REFERENCE* 2 Sheets-Sheet 1 Filed .June 1B. 1943{..w u x LV il ROM l. h.. n.. br nw www@ Y Nm 0% o. 0% bb Y moQU nEXAMINER 2.5 0 2 0 1 y cRoss REFERENCE June 3, 1947. H. BELAR ETALPHOTOELECTRIC CONTROL APPARATUS FOR DIAPHRAGMS Filed June 18, 1943 2Sheets-Sheet 2 Il @OX A INV To Herrlg BYnuZe a f4 UUR/VE L Patented June3, 1947 PHOTOELECTRIC CONTROL APPARATUS FOR DIAPHRAGMS Herbert Belar,Palmyra, and Emile C. Guedon, Audubon, N. J., assignors to RadioCorporation of America, a corporation of Delaware Application June 18,1943A, Serial No. 491,344

2 Claims.

This invention relates to light control apparatus and is particularlyconcerned with apparatus and controlling circuits for regulating theamount of light which is permitted to fall upon a light sensitivedevice.

For purposes of illustration, the invention will be particularly relatedto and described in connection with television apparatus wherein thereis included a light sensitive tube of the so-called camera type uponwhich an optical image-is focused. In apparatus of this type, andespecially in television apparatus wherein the socalled storage types ofscanning or camera tubes are utilized, an optical image is suitablyfocused upon a light sensitive electrode member, commonly known as themosaic element of the camera tube. This mosaic element in the cameratube, such as the type generally known as the Iconoscope and theOrthicon, builds up an electrostatic charge image or replica of theimpinging optical image, and the resultant electrical charge image isappropriately scanned by a scanning cathode ray beam to release signalenergy output to a suitable load circuit for actuating electro-opticalimage reproducing apparatus.

In camera tubes of the general types above named, wherein thesensitivity is relatively high, it becomes apparent that while it isextremely important to insure adequate and proper exposure of the mosaicelement to the impinging light image, it is extremely dangerous toover-expose the mosaic. It is particularly desirable that adequate, andyet proper, exposure be had for several reasons, among which are, thatthe scene lighting may vary within Wide limits, and frequently may bemuch brighter than is required for proper exposure. Also, the camera orscanning tube equipment may, in some instances, be directed almostdirectly toward the sun, as would be particularly evident in cases ofautomatic gunre control apparatus, where the camera equipment is mountedin an airplane and enemy aircraft are kept within the field of view ofthe scanning tube, and such attacking aircraft very -frequently endeavorto make attacks so as to be between the attacked plane and the sun.

Under such circumstances, without suitable control of the light enteringinto the camera tube, it will be apparent that the television tube maybe rendered practically useless if subjected to too much light because,with such great sensitivity of the tube, saturation effects result andit becomes impossible to resolve between high lights and low lights orbright spots and shadows.

2 Further than this, too much light upon the mosaic is apt to result inthe permanent injury, or at least impairment, thereof. l

The invention herein to be disclosed provides for ways and means bywhich the camera tube may be appropriately protected, and whereby, forconditions of' extreme bright light, the amount of light which ispermitted to enter into the camera tube is reduced but, for conditionsof reduced illumination, the amount of light which is permitted to enterupon or innuence the camera tube is increased.

To this end, an. appropriate iris control is provided by way of ashutter element which opens and closes under the control of anelectrical circuit operating in accordance with reductions and increasesin the amount of light available to inuence the camera tube. Foraccomplishing this objective, provision is made for the use of aseparate light sensitive element which is arranged toreceive a lightimage which is a substantial duplicate of that directed into the cameratube and of substantially equal brilliance. A light sensitive tube ofthis character is then connected appropriately with a suitable form ofamplifier and relay tube which provides for actuating a control motorwhich automatically serves to control the iris opening.

To this end, the motor is provided with a plurality of relay controlsoperated in such a way that for increases in light on the lightsensitive tube, the motor turns or operates, for instance, in aclockwise direction, while for decreases in the amount of light themotor may turn or operate in a counter-clockwise direction. The rotationof the motor is arranged thus to control the diaphragm opening bysimultaneously varying the opening through which the light on the lightsensitive control tube is projected, and simultaneously varying theopening through which the light of the same image is able to pass toinfluence the scanning tube.

In the arrangement disclosed, provision is also made whereby when themotor has been operated in one direction of motion for a predeterminedtime (or angle) an appropriate instrumentality stops the rotations inthat particular direction, but in no way affects the control in thereverse direction. When the light conditions change to the otherextreme, exactly the reverse conditions take place and the iris ordiaphragm is altered from one extreme to another in the oppositedirection.

VProvision is also made whereby, for a predetermined intermediate rangeof light chosen between a minimum opening and a maximum opening of thediaphragm or iris, for instance, the motor and its controls will remainineffective and yet, for a change in the impinging light at one of thetwo directions, the control shall be effective in one or the other abovedescribed ways.

It, accordingly, becomes an object of this invention to provide ways andmeans by which a light sensitive camera tube may have the amount,

of impinging light automatically set and controlled thereby to establisha predetermined signal level output for preestablished conditions ofillumination.

A further object of the invention is that o f providing a televisionscanning system and control wherein the scanning tube is protectedagainst extreme conditions of illumination which would tend either todestroy the tube or to destroy its efficiency of operation.

A further object of the invention is that of providing a control of thelight input to a scanning camera tube and to maintain a pre-establishedoutput level.

A further object of the invention is that of providing a light controlfor use with a light sensitive device which shall be capable of varyingthe amount of entering light in accordance with external conditions, andin which the time within which the control from one extreme to the othertakes effect is reduced substantially to a minimum.

Another object of the invention is that of providing ways and means bywhich a proper exposure of a light responsive film is made possible,irrespective of the brilliance of illumination of the scene beingviewed.

Another object of the invention is that of providing a control system inwhich the camera tube is automatically protected against excess light inthe event of failure of the amplifying circuits associated with it.

O ther, obiects o f the invention are those of providing a systemwhereby any desired or predetermined characteristic of light inputagainst scene lighting can be obtained for television or photographicsystems through the use of suitably controlled diaphragm and iriselements.

Other objects o f the invention are those of providing ways and means bywhich existing defects and disadvantages of prior art arrangements areovercome, while, at the same time, the control apparatus for achievingthese results is extremely simple and substantially foolproof in itscontrol.

Other objects of the invention will become apparent and at once suggestthemselves to those skilled in the art to which the invention isdirected, when the following description is read in connection with theaccompanying drawings, wherein:

Fig. l shows conventionally one form of control system with theelectrical circuit controlling a two-blade iris; and,

Fig. 2 shows a modincation, oi a portion of the circuit of Fig. 1.

Referring now to the drawings, and first to Fig, 1, it will be assumedthat light rays reflected from some suitable image area (not shown) passalong the substantially parallel paths conventionally designated as I--Iand 2-2, of which theforrner light path is in the direction of a lightresponsive photo-electrically active tube Il, and theI latter light pathis in the direction of a cameratube I3 which, for illustrative purposes,may be considered as either an Orthicon or CROSS REFERENCE "Iconoscopelocated within a conventionally represented camera tube housing. It isto be understood, in this connection, that the same, or substantiallythe same, light image is projected along each of the paths I-I and 2-2,and that, where desired,l appropriate correction for parallax distortionmay be provided.

Many and various ways and means to accomplsh the parallax correction inorder to assure that substantially the same optical image is projectedupon tubes I.I and I3 are known, but, as illustration of one ol suchforms, reference may be had to U. S. Patent No. 1,931,890, granted toBurns on October` 24, 1933.

4 Under such circumstances, the light of the optical image passing alongthe path I-I enters the light sensitive phototube II through the lens orother suitable optical element i5 While light rays, representative ofthe same optical image, enter into and affect the camera tube withinhousing I3 by being focused along a path 2-2 and directed upon the lightsensitive mosaic element of the camera by Way of the lens or othersuitable optical system I1.

Interposed in each of the light paths l-I and 2--2 are the blades I9 and21 of a shutter instrumentality which is pivoted at the pivot point 23in such a manner that two distinct openings, indicated by the area 25 inthe optical path to phototube II and the area 21 in the optical path tothe camera tube I3", are provided. It is apparent that, in the event theblades I9 and 2i move relative to one another about a pivot point 23,tbe openings 25 and 21 shall be made larger or smaller in accordancewith the direction of motion of the two blades.

To this end, and for the purpose of providing a control of such a naturethat the final control of the system approaches the action of a limiter,the output current from the phototube II is caused to control, in amanner later to be explained, the operation of a drive mechanism oiappropriate form to vary the area of the openings 25 and 2 1 and tomaintain the said openings of like size, or at least predeterminedproportional size, at all times, in order that the amount or brillianceor effect of the impinging light on each of the light sensitive elementsshall be suitably controlled.

Where the openings are of like size, the optical systems or lenselements I5 and I1 are preferably oi the same size and the same apertureand focal length, so that the resulting control, which is exercised byway of the phototube control I I, shall be an exact measure of theeffect produced upon the camera tube within the hou-sing I3.

With the arrangement as it is constituted and shown, the phototube IIincludestheusual photoelectrically responsive cathode element 29 and theassociated anode element ll. In accordance with the form oi arrangementillustrated, the anode element is maintained positive relative. to thecathode 29 by way of a suitable, connection through conductor 33v to anappropriately chosen point on the voltage divider 35, between theouterterminals of which a, suitable source of positive voltage is connectedat 3f!4 and` the negative terminal of the voltage supply source isconnected to ground at 4U'. Ifhevoltage supplysource may be of anydesired type andeither constituted by the suitable voltage divideroutput from a suitable alternating, current rectifier or may` be anappropriately chosen battery,

"Ihe cathueeiement :s or thapnototube, Il connects to the voltage supplysource (not shown) at ground 40 by way of the load resistor 39. Thisload resistor is suitably tapped at a desired point 4l, for instance,and supplies a. control potential upon the grid or control electrode 45of an amplifying tube 41 by way of the direct connection throughconductor 43. In order that the control voltage applied may beappropriately smoothed, a condenser 49 connects between controlelectrode 45 and ground 40 in known manner. The cathode element 5| ofthe amplifier tube 41 connects to the voltage divider 35 at anyappropriate point, such as 53, to provide the appropriate potential onthe cathode relative to the anode 55, which connects through the loadresistor 51 to the high potential terminal 31 of the applied voltagesource, as connected across the voltage divider element 35.

In order that further amplification of the resulting energy output ofthe iirst half of tube 41 may be had, there is direct connection fromthe anode element 55 to the grid or control electrode of the second halfof the tube. This second half of the tube has voltage supplied to theplate or anode element 6| through the serially connected relay coils 63and 65, which connect between plate or anode 6I and the terminal point31, where the positive end of the voltage supply source is connected.The cathode element 61 of the second half of the tube is appropriatelybiased by way of the connection to some suitable point on the voltagedivider 35, such as the point 69.

From what has been disclosed, it thus becomes apparent that two stagesof ampliiication of the output current from the phototube Il have beenprovided which, for purposes of illustration, are shown as having beenembodied within the single tube element 41. A tube of this charactermay, for instance, be one of the type known in the art as 12SN7, orother appropriate type provided for amplification purposes may be reliedupon; or, still further, the two stages of amplification may be providedby two completely separate tube instrumentalities.

When current flows through the output of the second half of tube 41, forinstance, it ows through the relay actuating coils 63 and 65 which serveto control the operation of the relay armatures 62 and 64, respectively,which are moved between the contact points 68 and 66 on the one hand,and 12 and 1U on the other hand. The armatures 62 and 64 are normallyset, as indicated, by the resilient or spring elements, so that, in thestate of deenergination of the relay coils 63 and 65, they rest againstcontact points 68 and 12, respectively.

Under conditions of energization of the coils, the relay armatures 62and 64 move respectively to contact against contact points 66 and 10. Itwill be noted that the contact points 68 and 10 each lead, respecively,to blind or unused terminal points, so that, in such positions of therelay armatures, no resulting control effects take place.

It also will be appreciated that, in the arrangement as it is hereindisclosed for illustrative purposes,- the relay armature 62 may beconsidered to be brought into operation when the current flowing throughthe relay 'winding 63 is of the order of 6 milliamperes, while the relayarmature 64 may be considered to be energized by way of the controlwinding 65 when the current flowing through the winding 65 is of theorder of approximately 4 milliamperes.

Thus, relay armature 62 (as well as armature 64) functions forconditions of high output current from the second half of tube 41, andrelay 6 armature 64 alone functions for conditions of lower outputcurrent from this tube.

Under these circumstances, it will be seen that a suitable source ofcontrol voltage for operating a motor element, conventionallyrepresented at 15, may be connected at terminal points 14 and 16, withthe positive terminal of the supply or control source (not shown) beingconnected, for instance, at terminal point 14, and the negativeconnected at point 16, or connected at ground 46. A connection is madefrom the terminal point 14 to each of the contact points 12 and 66, withthe armatures 62 and 64 connecting respectively by way of conductors 11and 19 to the switch contact elements 18 and 80.

Under normal conditions, and in the absence of anything to break thecontact, these contact elements 18 and 80, respectively, make contactwith the contact points 8| and 82, of which the former connects throughthe eld winding 83 of the motor 15, and the latter to the field winding84 of the same motor, 'with the two windings 83 and 84 being connectedfrom the common junction point by way of the low resistor 86 to ground40 andto negative terminal of supply voltage source 16.

It thus becomes apparent that with the relays in the position shown bythe diagram, current will flow from the positive terminal of the sourceconnected between points 14 and 16, through the relay contact 12, thearmature 64, the conductor 19, the contact armature 89, contact point 82and winding 84, and thence from the point through the motor armatureback to the negative terminal 16, or ground 40, so that the motor 15 isrotated in one direction of rotation. The armature may be shunted by aresistor, such as 86. This then causes the motor shaft, conventionallyrepresented as 81, to rotate in a corresponding direction and drive agear train (not shown) contained within the gear box 88 through a clutchmechanism conventionally represented at 89. When so driven, the geartrain within the gear box 88 is adapted to rotate (in an appropriatemanner) the blades of the iris member about the pivot point 23 by meansof gear elements so that one blade turns clockwise and the othercounter-clockwise.

At the same time, due to the rotation of the motor in the directionnamed, a limit switch control element 93 is driven from the shaft 81, sothat as it contacts the overhanging edge 9| of the contact strip B0 itcauses the contact between the contact member 80 and contact point 82 tobe broken, whereby the motor stops its rotation.

For the conditions above described, it will be appreciated that theseare circumstances representing the operational conditions when brightlights influence the phototube Il, in that the current output under suchcircumstances from the second half of the tube 41 is reduced and,therefore, it is desirable to close further the opening 25 through whichlight affects the phototube Il and reduce still further the outputcurrent to retain the equilibrium value.

However, suppose that this condition is maiutained and the motor 15turns in the direction chosen, it can be seen that the contact limitswitch element 90 soon rotates far enough to break the contact betweenthe contact strip 80 and contact point 82 so that the voltage supply tothe motor is broken and the motor thus must stop running. At the sametime, contact is main.- tained between contact member 8l and the contactstrip 18, so that if the output energy from CROSS REFERENCE the secondhalf of tube 41 increases above a value required to overcome the effectof the resilient means normally holding armatures 62 and 64 againstcontact points 68 and 12, it can be appreciated that the amature 62 willclose on contact 66 and amature 64 will close on contact 10.

Whether or not contact between point 82 and strip 80 is broken, currentto drive the motor in the opposite direction will ilow from terminalpoint 14 through the contact point 66 and armature 62, conductor 11,contact strip 18, contact point 8|, motor winding 83, point 85 and backthrough the motor amature to negative terminal 16, or ground 40, untilthe current ilowing in the second half of tube 41 is reduced to releaseamature 62. Also, as the motor turns in the opposite direction to thatfirst assumed at times when armature 62 contacts the point 66, it isapparent that the limit switch element 90 moves in such a direction thatcontact is again restored between the point 82 and the strip 80.

Thus, it can be seen that the opening of the limit switch, due torotation of the motor in one direction, does not in any way aiect theability or the possibility of driving the motor in the oppositedirection should conditions of light change in such a direction as tomake the opposite type oi aperture desirable.

From what has been stated above, it will be appreciated that if thelight falling upon the phototube I is of a value or intensity greaterthan that required to reduce the current ow in the second half of thetube 41 to a value less than that required to overcome the force of thespring member 1| which holds the armature 62 in contact with terminal68, whereby the armature 62 remains in contact with terminal point 68,and if this light is less in intensity than that required to reduce thecurrent in the second half of the tube 41 to a value which is requiredto maintain the armature 64 in contact with the terminal 10 against theforce of the spring member 13 normally holding it in contact with theterminal 12, then the circuit starting at the terminal point 14, whereatthe positive voltage is applied, is open and the motor 15 cannot run. Inother words, it becomes apparent that for predetermined light intensityand corresponding output currents from the second half of the tube 41,which are between the limits of the current flows required to actuatethe relay armatures 62 and 64, the motor 15 will not operate. In thisway, the iris members I9 and 2| will maintain the light impinging uponthe phototube Il, and also upon the camera tube I3, between set limitsduring any change in scene lighting, but where there is a momentarychange in the light intensity which tends to fall upon the camera tube,the motor will operate in one direction or the other to maintain theiris opening within the desired limited values.

Now, referring to the circuit modication shown by Fig. 2, the controlarrangement for applying a control voltage upon the grid or controlelectrodes of the tube 41 is essentially the same as shown and describedin connection with Fig. 1, and, accordingly, Fig. 2 shows only thatportion of the circuit beginning with the relay windings 63 and 65. Inthe modified arrangement of Fig. 2, the output current from the secondhalf of the tube 41 ows through the relay windings 63 and 65, asdescribed in connection with Fig. l, and, depending upon the currentflowing, the armatures 62 and 64, respectively, will be actuated.

It was explained, in connection with Fig. 1, that where extremely brightlights or high intensities of illumination fell upon the phototube lowercurrent output in the second half of the tube 41 would result. In thisway, for high lights, the current flowing through the output of thesecond half of tube 41 would be insuilicient to actuate the relayarmature 62 against the force of the resilient means 13 over towardcontact point 10.

In the de-energized state, the armatures 62 and 64, respectively, restagainst contact points 6I and 12. While in the energized state (as shownby Fig. 2) the armatures 62 and 64, respectively, contact the contactpoints 66 and 10, respectively. Normally the contact points 10 and 68are connected, and the contact points 12 and 66, respectively, connectby way of conductors |03 and |04 to ground 40, or to the negativeterminal 16 by way of connection through the contact point |01 and thecontact army |09, or contact point |06 and contact arm |08, with aconnection being made from the negative terminal 16 of the supply source(not shown) to ground by way of conductors |05. The armature members 62and 64 connect by way of conductors |0| and |00, respectively, to thebrushes of the motor 15, which has a permanent eld developed in themanner shown conventionally by the magnet |02. As the motor 15 rotates,it causes the limit switch element also to rotate in either a clockwiseor counter-clockwise manner, depending upon the direction of currentflowing through the motor.

As was explained in connection with Fig. l, the rotation of the limitswitch element 90 will cause the contact established between contactpoint |06 and the contact strip or arm |08 to be broken when limitswitch element 90 rotates in one direction, which may be assumed tocause an opening of the iris elements, whereas, if the limit switchelement 90 rotates in the opposite direction, contact will be brokenbetween contact point |01 and the contact arm or strip |09 in such a waythat the iris element will tend to close and reduce the light reachingeach of the phototube and the camera tube I3,

From the way in which Fig. 2 has been shown, it will be seen that acondition of low light on the phototube and the camera tube I3 isassumed, so that a maximum current output of the current flows from thesecond half of the tube 41, which provides maximum current through therelay windings 63 and 65. Thus, each of the relay armatures 62 and 64 isactuated and, in the arrangement shown, current will now now from thepositive terminal 14 through the contact point 10 to tle armature 64,and thence through the conductor |00, through the motor 15 and outthrough the conductor |0| and thence to contact point 66 and thearmature 62, from which the circuit follows through the conductor |04,the contact strip |08 and contact point |06 back to the negativeterminal 16 via the conductor |05 or to ground 4I from the contact point|06.

Under these circumstances, the limit switch 90 is rotated in a clockwisedirection, as long as the relay actuating current stays unchanged, untilthe iris opens to a maximum degree, and contact is finally brokenbetween contact point |08 and the contact strip or arm |08. Under theseconditions, it can be seen that for reduction in current output of thetube 41, which is insuiiicient to actuate armature 62 but whichmaintains armature 64 in position shown, the condition of brightnesscontrol will remain xed at its previous state, because there is now anopen circuit formed, in that the positive terminal of th'e source (notshown) connected at 14 connects to both EXAMlNER conductors and 0| byvirtue of the connection established between the armature B4 and thecontact point 10, and also between the armature 62 and contact point 68,which connects to contact -point 10, thus no current would flow throughthe motor.

However, let it be assumed that conditions change still further so thatthe light becomes very bright on the phototube I I and the camera tubeI3, in which condition the current output from the second half of tube41 becomes less and less, so that finally the current iiowing throughthe relay winding B5 is insuflicient to overcome the eiect of theresilient means 13, wh'ereupon the amature 64 now contacts point 12, andarmature 62 is upon contact point 68. Under these circumstances, it canbe seen that the motor will run in the opposite direction from thatabove described, because current now iows from the positive terminal ofthe source (not shown) connecting at contact point 12 through contactpoint 68, and the armature 62 and conductor |0I, and thence back throughth'e motor 15 and conductor |00 to the armature 64 and contact point 12,from which a connection is established by way of conductor |03 and thecontact strip or member |09 and contact point |01 back to negativeterminal 16 and ground 40 by way of conductor |05.

In this way, it can be seen that the current :dowing through the motorflows in the opposite direction from that direction in which' it owedfor relatively low intensity of illumination. The result is that thelimit switch element 90 now turns in a counter-clockwise direction and,if the conditions of high light persist, then it becomes' apparent thatthe connection between the contact strip or member |09 and the contactpoint |01 is broken and the iris elements are closed to the maximumdegree, so that the opening provided at the iris elements and 21(Fig. 1) is a minimum. However, for intermediate values of current flowor for conditions where the current flow is just sucient to actuatearmature 64 but insufficient to actuate armature 62, conditions ofintermediate opening are obtained.

As explained in the arrangement of Fig. l, the modication of Fig. 2 alsoso provides that for conditions where the apertures or openings 25 or 21have been closed to a limiting amount by way of the counter-clockwiserotation of the limit switch element 90, such closure in no wayprecludes operation of the motor in the reverse direction if the lightintensity is reduced, and, consequently, the iris opening may be madegreater even though there is, at the start of the reduced lightintensity condition, an open connection between contact strip |09 andthe contact point |01. However, under such conditions, since the motorrotates in a direction to rotate limit switch 90 in a clockwisedirection, contact is again established between contact strip or member|09 and contact point |01, and likewise, until the limit switch rotatesto a predetermined degree in the clockwise direction, contact will bemaintained between contact strip |08 and contact point |06.

It thus becomes apparent that the modification of Fig. 2, in somesenses, simplifies the arrangement shown by Fig. 1. Furthermore, fromthe circuit hereinabove described, it can be appreciated that if afailure of power supply for tube 41 should occur, the output currentflow will be reduced to a minimum, and consequently the system isprotected at all times, because minimum current output results forconditions of high light, and, therefore, if the power supply shouldfail, it will be appreciated that the relay armatures 62 and 64 occupysuch a position relative to th'e contact points 68 and 12, respectively,that the motor 15 tends to rotate in a direction such as to close theiris opening and, at the same time, turn the limit switch in acounter-clockwise direction. In this way, the camera tube containedwithin the housing I3 is at all times protected.

Although the particular construction of the iris elements themselvesforms th'e subject matter of a separate application, it is to be notedthat it is especially desirable that these elements, from a mechanicalstandpoint, be carefully balanced with regard to each other, so thatconsiderable ease of operation is obtained.

While the invention has been described herein as applicable and relatedto a television tube particularly, it will be appreciated that thesystem is likewise applicable to th'e ordinary type of camera equipment,such as a motion picture camera, wherein the camera tube, or the like,receives its light through the optical system I3 and the entering light,in contrast to its influence on the mosaic element of the televisiontube, iniuences a light sensitive photographic element to producethereon a latent image of the viewed subject, and, accordingly, it is tobe appreciated that the application of the invention, in its disclosedform, may have wide and varied uses, all of which fall fully within thesphere and scope of what is herein set forth.

Having described the invention, claimed is:

1. An optical system for television apparatus and the like for use inregulating the quantity of light directed to each of an optical imageresponsive target and a controlling photo-electric tube by way of anoptical system arranged to direct substantially like and equallybrilliant optical images simultaneously upon each of the target and thephotoelectric tube along adjacent optical paths comprising, incombination, a single rotatable multiple section diaphragm elementhaving a plurality of openings with one opening interposed in each ofthe optical paths for controlling the amount of light impinging uponeach of the said image responsive target and photoelectric tube, areversible motor element, a source of energy connected to said motor todrive the same, means to connect the diaphragm with the motor element toso operate the said diaphragm as to move it in the direction toward amaximum opening to pass greater light along each optical path with onedirection of motor rotation and to move it toward the direction of theminimum opening to reduce the light along each optical path with motorrotation in the opposite direction, a pair of serially connected relayelements connected to respond to the current flow through thephotoelectric control tube, one of said relays being connected torespond to current output levels to the photoelectric tube above apredetermined minimum value and the other of said relays being set torespond, jointly with the first-named relay, to current output levelsexceeding a selected maximum value, electrical connections between thesource and the motor through said relays so that current output levelsfrom the photoelectric tube below the selected minimum response level ofone of the relays causes the current to be supplied from the source tothe motorto rotate it in a direction to open the diaphragm to admit agreater quantity of light upon each of the target and the photo- What'1S :mangue .electric control tube and .for currentoutput levels fromthe photoelectric control tube greater than theselected maximum relayresponse level of the other relay a current is supplied from the sourceto the .motor in a direction to so rotate it as to move the diaphragm inthe direction of closure and to reduce the light reaching the target andthe photoelectric tube and further electrical connections provided bythe said relays and eiected Aat time periods when the photoelectric.control tube output currents are of a value intermediate the selectedmaximum and minimum relay response levels to interrupt and break theconnection between the energy source vand the motor to arrest motorrotation.

2. An optical system for television apparatus and the like for use inregulating the quantity of light directed to each of an optical imageresponsive target and a controlling photoelectric tube by Way of anoptical system arranged to direct substantially like and equallybrilliant optical images simultaneously upon each of the target and thephotoelectric tube along adjacent optical paths comprising, incombination, a single rotatable multiple section diaphragm elementhaving a plurality of openings with one opening interposed in each ofthe optical paths for controlling the amount of light impinging uponeach of the said image responsive target and photoelectric tube, areversible motor element, a source of energy connected to said motor todrive the same, means to connect the diaphragm with the motor element toso operate the diaphragm as to move it in the direction toward a maximumopening to pass greater light along each optical path with one directionof motor rotation and to move it toward the direction of the minimumopening to reduce the light along each optical path with motor rotationin the opposite direction, a pair of serially connected relay elementsconnected to respond to the current flow through the photoelectriccontrol tube, one of said relays being connected to respond to currentoutput levels to the photoelectric tube above a predetermined minimumvalue and the other of said relays being set to respond, jointly withthe rst-named relay, to current output levels exceeding a selectedmaximum value, electrical connections between the source and the motorthrough said relays so that current output levels from the photoelectrictube below the selected minimum response level of one of the relayscauses the current to be supplied from the source to the motor to rotateit in a direction to open the diaphragm to admit a greater quantity oflight upon each of the target and the photoelectric control tube and forcurrent output levels from the photoelectric control tube greater thanthe selected maximum relay response level of the other relay a currentis supplied from the source to the motor ina direction to so rotate itas to move the diaphragm in the direction of closure and to reduce thelight reaching the target and the photoelectric tube, further electricalconnections provided by the said relays and effected at time periodswhen the photoelectric control tube output currents are of a valueintermediate the selected maximum and minimum relay response levels tointerrupt and break the connection between the energy source and themotor to arrest motor rotation, and a switching means connected with themotor to open the established connection between the energy source andthe said motor upon the attainment of selected degrees of rotation ofthe motor coinciding with selected maximum and minimum diaphragm openingpositions.

HERBERT BELAR. EMILE C. GUEDON.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,854,892 Ewend Apr. 19, 19322,307,479 Annick Jan. 5, 1943 363,547 Schneider May 24, 1887 FOREIGNPATENTS Number Country Date 821,026 France v-- Aug. 17, 1937 '491,410Great Britain Sept. 1, '1938 487,240 Great Britain June 16, 1938 503,901Great Britain Apr. 17, 1939 763,279 France Feb. 12, 1934

